1. Field of the Invention
The present invention relates to a method of manufacturing a toner, the toner produced using the method, developer containing the toner and an image forming apparatus using the toner.
2. Discussion of the Background
In an image forming apparatus for use in Electrophotography and similar areas, a toner is used as a developer (either one-component or two-component developer) to develop an electrostatic image. Typically, such a toner is manufactured by melting, mixing and dispersing a release agent, a colorant, and a charge controlling agent in a thermoplastic resin as the main component followed by uniforming, pulverizing and classifying the resultant. A toner manufactured by such a pulverization method has excellent characteristics in some degree. Recently, a toner having a small particle diameter and a sharp particle size distribution has been demanded to obtain images with high definition, good sharpness, and high gradation. To satisfy these demands using a pulverized toner, a classification process is additionally needed in which the pulverized toner is classified to achieve a sharp particle size distribution. To obtain a toner beyond the ability of a typically pulverized toner for an image having a high definition, fine toner particles having a particle diameter not greater than 5 μm and coarse particles having a particle diameter not less than 20 μm are removed. As a result, it is inevitable that the toner yield is extremely low.
In recent years, to overcome these problems involved in the pulverization method, a toner manufacturing method such as a suspension polymerization method has been proposed. A typical suspension polymerization method is as follows: melt, mix or disperse a polymeric monomer, a colorant, a release agent, a polymerization initiator and a dispersant to obtain an oil phase; put the oil phase in an aqueous phase (water or a mixture of water and a dispersion stabilizer or a thickening agent for use in viscosity adjustment); and impart a high shearing force to the resultant to prepare an O/W emulsion (hereinafter referred to as emulsified dispersion liquid) for polymerization to granulate colored polymeric particles (toner). Different from the pulverization method, this suspension polymerization method disperses release agent, colorant, etc., in a solvent having a low viscosity. Therefore, it is possible to obtain a toner having a more uniform composition and a sphere form. In addition, a polymerized toner having a sharp particle size distribution can be obtained at a high yield ratio by the suspension polymerization method.
As a method of manufacturing a toner based on these polymerization methods, unexamined published Japanese patent application No. H10-195205 describes a manufacturing method in which a toner component is turned into fine droplets or particulates by a high speed shearing device and these fine droplets and particulates are polymerized to obtain a resin particle.
However, the method in which fine droplets and particulates (hereinafter referred to as emulsified primary particles) are continuously manufactured by a high speed shearing device, introduced into a tank or a facility in the next process and cohered or agglomerated by stirring to obtain an objective particle has a drawback. That is, behaviors of fluid and particles of emulsified primary particles in the pipes to the tank have a great impact on the particle diameter of the finally obtained particle. This leads to production of coarse particles, deterioration of particle size distribution and non-uniformity of the toner composition.
Accordingly, a need exists for a method of manufacturing a toner by which the production of coarse particles and deterioration of particle size distribution can be restrained and the composition of the toner obtained can be made more uniform.